Optical access technology provides large bandwidth and high reliability, and is a development direction of the access technology. PON is one of the major technologies of optical access, where A/BPON, EPON and GPON have been utilized in large scale.
With the rapid development of data services, the mobility requirement of data access has emerged constantly, and the wired and wireless integration will meet the experiences of users better. With full-service access capability of data, voice and Time Division Multiplex (TDM), PON technology can meet wireless access demand in constant evolution. Especially in the access applications of micro-cells and home base stations, the convergency characteristic of PON makes the entire network clear in levels, convenient in construction, efficient in management.
The mobile base stations of CDMA2000, TD-SCDMA and WiMAX etc. have strict requirement on time synchronization. Some value-added services provided by the mobile network also need strict time synchronization. At present, the wireless time service means, such as GPS etc., are mainly used on mobile base stations. In the construction of high quality wireless networks, time service using wired networks has great significance both in economy and in stability.
In the process of IP-based network, the Precision Time Protocol (PTP) of network of IEEE1588 has been widely used in wireless base station. But PTP protocol works better in the condition of symmetric delay in the uplink and downlink of a network, and asymmetric nodes needs to be processed if it is an asymmetric network. PON is an asymmetric network for delay in the uplink and downlink, complicated flow processing, and excessive protocol workload and excessive network bandwidth occupancy occur when PTP protocol is dealt with in PON.